JP2014103682A - Method and apparatus for lte radio link failure determination in drx mode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate rapid detection of a radio link failure (RLF), which is important in order to initiate radio link or WTRU recovery procedures in a timely manner since malfunction and dysfunction of the radio link, that is, the link between a WTRU and an eNB, may occur due to various reasons such as, for example, shielding, fading, interference or other mishaps due to mobility.SOLUTION: Service data is transmitted in a wireless communication system. A method and apparatus for detecting radio link failure (RLF) in a wireless transmit receive unit (WTRU) in a cell of the system includes the WTRU performing a series of radio link measurements during a discontinuous reception (DRX) on-duration, comparing each of the series of radio link measurements to a threshold, and determining that the series of radio link measurements indicates an out-of-synch condition.

Description

  The present invention relates to wireless communication.

  Third Generation Partnership Project (3GPP) brings new technologies, new network architectures, new settings, and new applications and services to wireless networks to provide improved spectral efficiency and a faster user experience , Has started a program for Long Term Evolution (LTE).

  FIG. 1 shows an overview of a conventional terrestrial radio access network (E-UTRAN) 100 of an extended universal mobile communication system (UMTS). As shown in FIG. 1, the E-UTRAN 100 includes three eNodeBs (eNBs) 102, but any number of eNBs can be included in the E-UTRAN 100. The eNBs 102 are connected to each other via the X2 interface 108. The eNB 102 is also connected to an extended packet core (EPC) 104 by an S1 interface 106, which includes a mobility management entity (MME) 108 and a serving gateway (S-GW) 110.

  FIG. 2 shows an LTE user plane protocol stack 200 according to the prior art. The protocol stack 200 is placed in a wireless transmit / receive unit (WTRU) 210 and includes a packet data control protocol layer (PDCP) 202, a radio link control layer (RLC) 204, a media access control layer (MAC) 206, and a physical layer (PHY). 208 is included. The protocol stack 200 may be in an eNB (not shown).

  FIG. 3 shows an LTE control plane protocol stack 300 of the WTRU 210 of FIG. The control plane protocol stack 300 includes a non-access layer (NAS) 302 and a radio resource control (RRC) 304. The control plane protocol stack 300 also includes PDCP 306, RLC 308, and MAC 310, which together form a layer 2 sublayer 312.

  Wireless link, ie link malfunction between WTRU and eNB (also referred to as malfunction) and malfunction (also referred to as dysfunction) may be caused by other factors due to shielding, fading, interference, or mobility, for example. It may occur for various reasons such as an accident. In order to initiate a radio link or WTRU recovery procedure in a timely manner, rapid detection of radio link failure (RLF) is important. Typically, RLF detection involves downlink signal measurements made at a physical layer entity combined with event filtering so that the WTRU determines the next action sequence after a problem is detected. Can do.

  While performing the downlink measurement, the WTRU physical layer (PHY) entity (Layer 1) sends the “out-of-sync” or “in-sync” measurement results to the RRC entity. Can be configured to inform. The WTRU is configured to count the number (number) of out-of-sync results. The number of out-of-synchronization results can be counted by, for example, a counter such as the counter N310. When the RRC entity counts out of sync results a specific number of times, the RRC entity in the WTRU is configured to start a timer. For example, the WTRU may start a timer referred to as a T310 timer. If the T310 timer expires before being stopped for another reason, the WTRU is configured to determine that an RLF has occurred.

  FIG. 4 shows a cycle 400 of discontinuous reception (DRX; also referred to as discontinuous reception) according to the prior art. For LTE compliant WTRUs and eNBs, a connection state DRX has been introduced for power saving purposes, in particular to save WTRU batteries. When in connected state DRX mode, the WTRU may “shut down” for a period of time to reduce power usage. As shown in FIG. 4, during a DRX cycle (402, 404, 406), the WTRU may transmit and receive during an on-duration (also referred to as an ON period) (408, 410, 412), Neither transmission nor reception is performed during the sleep period (also referred to as a sleep period, a sleep period, or a sleep period) (414, 416, 418). Since the eNB can synchronize with the WTRU's DRX cycle, it does not transmit or expect to receive communications while the WTRU is in the sleep period.

  Three parameters can be used by the WTRU and the eNB to define the WTRU's DRX cycle. The DRX on / off, DRX period, and non-DRX timers may be assigned values that can be used by the network component to determine the WTRU's DRX cycle.

  An LTE compliant WTRU may also be configured to operate in multiple states, each state generally defining how the WTRU can function. The RRC_connected state is one of a set of predefined states that the WTRU can function. When in the RRC_connected state, the WTRU may also be configured to operate in DRX mode.

  If the WTRU is configured by the network to operate in DRX mode when in the RRC_connected state, the WTRU will be configured not to make downlink measurements for RLF during the sleep period portion of the DRX cycle. The WTRU will be configured to make downlink radio signal measurements for RLF only during the DRX on and active periods.

  A method and apparatus for detecting radio link failure (RLF) in a WTRU is disclosed. The method and apparatus includes a WTRU performing a series of radio link measurements during a discontinuous reception (DRX) on period, comparing each of the series of radio link measurements to a threshold, and the series of radio link measurements out of synchronization. Determining that the state is indicated. The WTRU may start a timer and continue a series of radio link measurements during the DRX sleep period. The WTRU may determine that the timer has expired and stop a series of radio link measurements.

  A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings wherein:

  As described above, the present invention provides a method and apparatus for detecting radio link failure (RLF) in a WTRU.

1 is a diagram illustrating an overview of an extended universal mobile communication system (UMTS) terrestrial radio access network (E-UTRAN) 100 according to the prior art. FIG. 2 is a diagram illustrating an LTE user plane protocol stack 200 according to the prior art. FIG. 3 shows a protocol stack 300 of the LTE control plane of the WTRU 210 of FIG. FIG. 3 shows a WTRU DRX cycle according to the prior art. FIG. 1 illustrates an example wireless communication system that includes multiple WTRUs and eNBs. FIG. 3 is a functional block diagram of the WTRU and eNB of FIG. 2. FIG. 6 illustrates a method for determining RLF according to one embodiment. FIG. 5 is a diagram illustrating a method of RLF detection according to another embodiment. It is a figure which shows the method of RLF detection by another embodiment.

  As referred to below, the term “wireless transmit / receive unit (WTRU)” includes but is not limited to user equipment (UE), mobile station, fixed or mobile subscriber unit, pager, cellular telephone, personal digital assistant (PDA) Computer, or any other type of user device capable of operating in a wireless environment. When referred to below, the term “base station” refers to, but is not limited to, a Node-B, site controller, access point (AP), or any other type of interface device capable of operating in a wireless environment. Including.

  FIG. 5 is a diagram illustrating a wireless communication system 500 that includes multiple WTRUs 510 and eNBs 520. As shown in FIG. 5, the WTRU 510 is in communication with the eNB 520, and the eNB 520 may be in communication with each other as shown in FIG. Note that although FIG. 5 shows three WTRUs 510 and one eNB 520, the wireless communication system 500 may include any combination of wireless and wired devices.

  FIG. 6 is a functional block diagram 600 of the WTRU 510 and eNB 520 of the wireless communication system 500 of FIG. As shown in FIG. 6, WTRU 510 is in communication with eNB 520. The WTRU is configured to function in DRX mode or non-DRX mode. The WTRU may also function in the RRC_connected state or the RRC-Idle state. The WTRU may be configured to perform the RLF determination method in DRX mode and non-DRX mode.

  In addition to the components found in a typical WTRU, the WTRU 510 includes a processor 615, a receiver 616, a transmitter 617, and an antenna 618. The processor 615 is configured to perform a method for determining the RRC_connected state and determining the RLF in the DRX mode. Receiver 616 and transmitter 617 are in communication with processor 615. Antenna 618 is in communication with both receiver 616 and transmitter 617 to facilitate transmission and reception of wireless data.

  In addition to the components found in a typical base station, eNB 520 includes a processor 625, a receiver 626, a transmitter 627, and an antenna 628. The processor 625 is configured to perform a method for determining the RRC_connected state and determining the RLF in the DRX mode. Receiver 626 and transmitter 627 are in communication with processor 625. Antenna 628 is in communication with both receiver 626 and transmitter 627 to facilitate wireless data transmission and reception.

  FIG. 7 is a diagram illustrating a method 700 for determining RLF according to one embodiment. Each DRX cycle (702, 704, 706) includes an on period (708, 710, 712). Measurements (714-732) can be made during each on-period (708, 710, 712). Each measurement result (714 to 732) is compared with threshold values Qin and Qout. Qin is a threshold value for the synchronization establishment operation, and is defined as a level at which reception is possible with significantly higher reliability than when the downlink radio quality is a threshold value for synchronization loss (Qout). Qout is a threshold for out-of-synchronization and is defined as a level at which a downlink radio link cannot be reliably received. The RLF evaluation may be based on the number of Qin and Qout results received by the PHY entity and sent to the higher layer entity.

  As shown in FIG. 7, in the first on-period 708, the first measurement 714 clears the synchronization established (Qin) threshold, while the second measurement 718 and the third measurement 720 are out of synchronization (Qout) thresholds. Did not reach. As a result, it is determined that the first DRX cycle 702 is out of synchronization. In the second DRX cycle 704, during the second on-period 710, it is determined that the first measurement 722, the second measurement 724, and the third measurement 726 are each out of synchronization. In the third DRX cycle 706, during the third on-period 712, it is determined that the first measurement 728, the second measurement 730, and the third measurement 732 are each out of synchronization.

In FIG. 7, the WTRU is operating in DRX mode in the RRC_connected state. RLF evaluation can be based on the measurement state of a predetermined number of consecutive DRX on periods (N _{RLF-durations} ) rather than evaluating the measurement results over a longer continuous period. As shown in FIG. 7, N _{RLF-durations} is equal to 3, and the RLF analysis is based on the measurement result of the first DRX cycle 702 (out of synchronization), the measurement result of the second DRX cycle 704 (also out of synchronization), And can depend on the measurement result (also out of sync) of the third DRX cycle 706.

N _{RLF-durations} can be determined based on several criteria. For example, N _{RLF-durations} may be a fixed number preset in the WTRU or notified from the network. N _{RLF-durations} may be, for example, a counter value such as N313 or a value obtained by dividing the counter value by an integer M, where M is a value obtained by dividing a timer value by an on period. N _{RLF-durations} is a function of the length of a timer, such as timer T310, as reported by the WTRU, as reported as N _{RLF-durations} = (T310 / on duration) Alternatively, the length of the on-period timer may optionally be included as a function of DRX cycle length, eg, media access control (MAC) DRX cycle, long DRX cycle, and short DRX cycle.

The length of the on-period timer can be set in the network and transmitted to the WTRU. The length of the on period timer may be calculated by the WTRU. The DRX cycle length used for calculating the RLF and the number of measurement results in the continuous on period may be inversely proportional. Optionally, N _{RLF-durations} can be equal to (set DRX length) / (shortest settable DRX length). As another option, N _{RLF-durations} can be equal to DRX length / W, where W is a network-configured or pre-configured integer.

  Referring again to FIG. 7, for each on duration (708, 710, 712) of each DRX cycle, the higher layer entity of the WTRU may receive a measured RLF value from the (PHY) entity. The PHY entity may evaluate and determine whether the WTRU is synchronized with the network or out of sync on a DRX cycle basis. The PHY entity then does not pass measurement data, but does “synchronize” or “out of sync” to higher layers such as a MAC layer entity, radio resource control (RRC) layer entity, or radio link control (RLC) layer entity. You can send a message to show. The PHY entity transmits the synchronization established state or the out-of-synchronization state by determining whether the measurement result of establishment of synchronization or the measurement result of loss of synchronization occupies the majority over the measurement period. If the number of measurement results is the same, the measurement result returned last is used to determine whether to pass an out-of-synchronization state or a synchronization establishment state to the upper layer.

  Referring again to FIG. 7, for the first DRX cycle 702, the PHY entity has two out-of-sync measurement results (718, 720) and only one out-of-sync measurement result (714), so It can be determined that an out-of-sync condition should be sent to the layer. Similarly, for the second DRX cycle 704 and the third DRX cycle 706, all the measurement results in each cycle are out of sync, so the PHY entity will send an indication of out of sync status (indication). .

The WTRU may be configured to determine that an RLF condition exists only when the measurement result of the DRX cycle that includes all N _{RLF-durations} on periods or on periods is out of synchronization. The RRC can be configured to handle DRX mode WTRUs in the same manner as when a timer such as the T310 timer expires and the WTRU is in non-DRX mode. As if the WTRU was in non-DRX mode after a timer such as the T310 timer expired, the RRC can be configured to handle DRX mode WTRUs.

  When the WTRU is in DRX mode, RLF measurements may be discontinuous due to the nature of DRX operation. For WTRUs in DRX mode, the PHY layer entity may be configured to implicitly use different Qout and Qin thresholds than when the WTRU is in non-DRX mode. For example, if the WTRU is in DRX mode, the PHY layer entity may apply an offset to a threshold that the WTRU can use in non-DRX mode. This offset can lower the Qout and Qin thresholds. A lower Qout threshold means that the measurement required to declare an out-of-sync condition in DRX mode is lower than in non-DRX mode. A lower Qin threshold means that the DRX mode can meet the measurement of establishment of synchronization more easily than the non-DRX mode. Therefore, in the DRX mode, the requirement for reaching the synchronization establishment state is looser than in the non-DRX mode.

  The WTRU may make another adjustment to determine the RLF state during the DRX mode. During the DRX mode, the PHY entity can be configured to reduce its filtering time from the non-DRX mode time to the length of the on period or less if the on period is shorter than the non-DRX filtering timer. . For example, if the non-DRX filtering time is 200 ms, in DRX mode, the WTRU may use a time shorter than 200 ms. This adjustment can be made by the WTRU, either signaled from the network or predefined, based on an offset, or by a rational or numerical value. The short DRX mode filtering time should be sufficient for the WTRU to make measurements and check the downlink radio link quality of the serving cell.

  Alternatively, while in DRX mode, the PHY entity monitors all radio frames and monitors the radio quality of the downlink only during the on period, measured over several (m) DRX periods. May be configured to be examined and measured against thresholds (Qout and Qin). The number m is a parameter notified from the network or a parameter derived by the WTRU based on channel conditions. If the on period is less than one frame, the WTRU may be configured to evaluate the link quality over only that on period.

  In another embodiment, measurements are taken during the on period of each DRX cycle. The WTRU may continue to measure even after entering the sleep period portion of the DRX cycle past each on-period boundary. This can occur when one or a preset low number of consecutive Qout measurement results are detected. If the average value of all measurements made during the on-period is less than the out-of-sync threshold, the WTRU sleeps until a set number of consecutive Qin is measured or RLF is declared. Measurement may be continued during the period. The DRX logic for data reception can be left unchanged.

  The WTRU may be configured such that when a set number of consecutive Qouts are detected, the RLF measurement operation continues during the sleep period as if the WTRU were operating in non-DRX mode. Thus, even when the WTRU is in DRX mode, a non-DRX RLF detection criterion that measures RLF determination using a network setup time such as RLF recovery timer T310, for example, can be used. However, if the synchronization establishment condition is satisfied before or after the length of the evaluation period, for example, 200 ms is completed, for example, when a set number of consecutive Qin is detected, in the inactive portion of the DRX cycle time, RLF measurement can be stopped.

  FIG. 8 illustrates a method 800 for RLF detection according to another embodiment. In the first DRX cycle 802, three measurements (804, 806, 808) are performed during the first on-period 810. In the second DRX cycle 812, three measurements (814, 816, 818) are performed during the second on-period 820, and three measurements (822, 822) are performed during the sleep period 828 of the second DRX cycle 812. 824, 826). Here, it is assumed that there is a possibility that the error occurs because the measurement result of out of synchronization is detected three times in succession. In the third DRX cycle 830, three measurements (834, 836, 838) are performed during the third on-period 832.

  In an alternative embodiment, if the WTRU is in DRX mode and a certain number of out-of-sync measurements are detected, the WTRU may start a timer for recovery. The WTRU may continue RLF measurements during the sleep period of the DRX cycle. The time required for the recovery measurement can be proportional to the number of synchronization establishment measurement results (number of times) required for radio link recovery or the duration of one synchronization establishment measurement. When a predetermined number of Qout measurement results are detected, the RLF measurement can be continued even during the recovery period. The recovery period is the period used by the WTRU to determine whether the measurement results are improving or remain out of sync. If it is determined that the measurement results are synchronized during the recovery period, the radio link has already improved. If it is not determined that synchronization is established, the WTRU may determine that RLF has occurred.

  Alternatively, the measurement may continue until the timer expires. This is because timer expiration means RLF. For example, the number of measurements performed during the sleep period (referred to as “recovery measurement” (Nr)) each has a period Dr, and there is a Tr interval between measurements, Nr × Dr = K X (counter value) x Tinsync (formula 1), K is a predetermined constant, and Tinsync is the time required for the synchronization establishment measurement. Furthermore, Tr = timer value / Nr. When Tr is equal to or less than Dr, recovery measurement is continuously performed. The timer value is allowed for the upper layer entity filter to receive several (counter value) consecutive synchronization establishment signals from the PHY entity to cancel out-of-sync condition of the radio link before the RLF is determined. It is a period.

  The WTRU may use an out-of-sync counter while in DRX mode. The value of the out-of-synchronization counter may depend on the RLF timer used in the DRX mode and the number of synchronization establishment instructions or the number of out-of-synchronization instructions sent from the PHY entity to the higher layer entity in each DRX cycle. For example, the DRX mode out-of-sync counter can be equal to ((DRX mode timer value) / (DRX cycle length)) × (number of instructions (Nsigns−Ll)). The DRX mode timer value may be equal to the non-DRX mode timer value plus the DRX cycle length.

  Nsigns-L1 can be determined by the value of the on-period timer and the DRX cycle length. For a WTRU with a short DRX cycle length, Nsigns-L1 can be equal to one. For a WTRU with a long DRX cycle length, Nsigns-L1 can be equal to the long cycle length divided by the short cycle length. For DRX mode, the synchronization establishment counter can be based on the number of out-of-synchronization timers plus a constant or the number of out-of-synchronization timers minus a constant.

  The WTRU reads the reference signal (RS) quality or physical downlink control channel (PDCCH) block error rate (BLER) during the sleep period and uses it as a measure of the RS quality or PDCCH BLER performed prior to the DRX sleep period. When comparing, the WTRU may determine that radio link quality and DRX cycle may not affect RLF detection time.

  The WTRU may monitor the PDCCH, which is a cell radio network temporary identifier (C-RNTI), a system information radio network temporary identifier (SI-RNTI), a paging radio network temporary identifier (P-RNTI). And decoding all other relevant RNTIs during the active period of the DRX cycle. Monitoring can be triggered when the WTRU detects an out of sync measurement result for a particular DRX cycle. If the RNTI is successfully decoded, the PHY entity can send an indication of synchronization establishment to the higher layer entity. If the RNTI decryption fails for a certain number of attempts due to, for example, a CRC failure, the PHY entity can send an out-of-sync indication to the upper layer.

  FIG. 9 illustrates a method 900 for RLF detection according to yet another embodiment. In step 902, the radio link status counter is set to the value of a parameter such as RADIO_LINK_TIMEOUT. This parameter can be pre-defined and is related to the number of out-of-sync signals needed for the WTRU to determine the RLF. At step 904, the upper layer entity filter receives the radio link monitoring indicator, and at step 906, the radio link status counter is updated according to the values in Table 1. In step 908, which is performed in each DRX cycle, the WTRU reads a radio link status counter. If the radio link status counter is not equal to zero, the process proceeds to step 902. If the radio link status counter is equal to zero, at step 910, the WTRU may determine that an RLF has occurred, or the WTRU may start a recovery timer.

  Table 1 can be modified by giving larger or smaller weights to the measurement results, or by giving larger or smaller weights to the DPCCH supervisory code. Further, in order for the WTRU to obtain a constant estimated PDCCH BLER, the PDCCH BLER can be based on the shortest PDCCH format or the maximum aggregation level.

For radio link recovery, i.e. (N <N _{RLF-durations)} when pieces of desynchronization instances (cases) were reported, WTRU, the number slightly smaller than N _{RLF-durations} pieces or N _{RLF-durations} Can be requested for link recovery.

  Embodiment

  1. A method for radio link failure (RLF) in a radio transceiver unit (WTRU), comprising performing a series of radio link measurements during discontinuous reception (DRX) on period, and each of the series of radio link measurements as a threshold A method comprising: comparing and determining whether a series of radio link measurements indicate an out-of-sync condition.

  2. 2. The method of embodiment 1 further comprising starting a timer and continuing a series of radio link measurements during the DRX sleep period.

  3. 2. The method of embodiment 1 further comprising determining that the timer has expired and stopping a series of radio link measurements.

  4). 4. The method as in any one of embodiments 1-3, further comprising determining a number of measurements for a series of radio link measurements.

  5. The method of embodiment 4 further comprising the step of determining the number of measurements during the sleep period based on the time required for measurement, the time required for synchronization establishment measurement, the counter value, and the constant.

  6). [0069] 6. The method as in any one of embodiments 1-5, further comprising the WTRU determining a reference signal quality to determine a radio link failure.

  7). [0069] 7. The method as in any one of embodiments 1-6, further comprising the step of the WTRU determining a downlink channel block error rate to determine a radio link failure.

  8). 8. The method as in any one of embodiments 1-7, further comprising the step of the WTRU decrypting a radio network temporary identifier (RNTI).

  9. A method of detecting a radio link failure in a wireless transceiver unit (WTRU), the step of setting a status counter to a certain value, the step of receiving a radio link monitoring index, and a status counter based on the value obtained from a lookup table A method of determining whether a counter value is equal to zero and determining whether a radio link failure has occurred.

  10. [0069] 10. The method of embodiment 9 wherein the look-up table includes values based on radio link measurements and downlink control channel monitoring.

  11. A wireless transmit / receive unit (WTRU) configured to determine a radio link failure, wherein the measurement unit is configured to perform a series of radio link measurements during a discontinuous reception (DRX) on period; And a processor configured to compare each series of radio link measurements with a threshold and determine whether the series of radio link measurements indicate an out-of-sync condition. WTRU.

  12 12. The WTRU of embodiment 11 further comprising a timer, wherein the processor is further configured to start the timer, and the measurement unit is further configured to continue a series of radio link measurements during the DRX sleep period.

  13. 13. The WTRU of embodiment 12, wherein the processor is further configured to determine whether the timer has expired and to stop the series of radio link measurements.

  14 14. The WTRU as in any one of embodiments 11-13, wherein the processor is further configured to determine a number of measurements for a series of radio link measurements.

  15. 15. The WTRU of embodiment 14 wherein the processor is further configured to determine the number of measurements during the sleep period based on the measurement duration, the duration of the synchronization establishment measurement, the counter value, and the constant.

  16. 16. The WTRU as in any one of embodiments 11-15, wherein the processor is further configured to determine a reference signal quality to determine a radio link failure.

  17. [0060] 17. The WTRU as in any one of embodiments 11-16, further comprising the WTRU determining a downlink channel block error rate to determine a radio link failure.

  18. 18. The WTRU of embodiment 17, further comprising the WTRU decrypting a radio network temporary identifier (RNTI).

  19. A wireless transmit / receive unit (WTRU) configured to detect a radio link failure, setting a status counter to a value, receiving a radio link monitoring indicator, and setting the status counter based on a value obtained from a lookup table A WTRU comprising a processor configured to update, determine whether a counter value is equal to zero, and determine whether a radio link failure has occurred.

  20. 21. The WTRU of embodiment 19 wherein the look-up table includes values based on radio link measurements and downlink control channel monitoring.

  Although features and elements have been described above in specific combinations, each feature or element can be used alone without other features and elements, or in various combinations with other features and elements, Or it can be used in various combinations without using other features and elements. The methods or flowcharts provided herein can be implemented as a computer program, software, or firmware embedded in a computer readable storage medium for execution by a general purpose computer or processor. Examples of computer readable storage media include read only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and CD- Optical media such as ROM discs and digital versatile discs (DVDs) are included.

  Suitable processors include, by way of example, general purpose processors, special purpose processors, conventional processors, DSPs (digital signal processors), multiple microprocessors, one or more microprocessors associated with the DSP core, controllers, microcontrollers, ASICs. (Application Specific Integrated Circuits), FPGA (Field Programmable Gate Array) circuits, and other types of ICs (Integrated Circuits) and / or state machines.

  Implements a radio frequency transceiver for use in a WTRU (Radio Transmit / Receive Unit), UE (User Equipment), terminal, base station, RNC (Radio Network Controller), or any host computer using a processor associated with the software can do. The WTRU may be used with modules implemented as hardware and / or software, such as cameras, video camera modules, video phones, speaker phones, vibrating devices, speakers, microphones, television transceivers, hands Free headset, keyboard, Bluetooth (registered trademark) module, FM (frequency modulation) wireless unit, LCD (liquid crystal display) display device, OLED (organic light emitting diode) display device, digital music player, media player, video game player module, An internet browser and / or any WLAN (wireless local area network) or UWB (ultra-wideband) module.

  The present invention is generally applicable to a wireless communication system.

102, 520 eNB
202, 306 PDCP
204, 308 RLC
206, 310 MAC
208 PHY
302 NAS
304 RRC
510 WTRU
615, 625 Processor 616, 626 Receiver 617, 627 Transmitter

Claims (8)

A method for determining a radio link failure (RLF) in a radio transceiver unit (WTRU) comprising:
Performing a series of radio link measurements in discontinuous reception (DRX) mode;
Detecting a predetermined number of consecutive out-of-sync conditions based on the series of radio link measurements;
Starting a timer upon detecting the predetermined number of consecutive out-of-sync conditions;
Continuing the series of radio link measurements using an evaluation period corresponding to non-DRX mode until the timer expires or stops while operating in DRX mode;
The method is characterized in that the timer is stopped upon detecting a predetermined number of consecutive synchronized states based on the continued series of radio link measurements. Detecting synchronization establishment based on the series of radio link measurements;
Stop the timer,
The method of claim 1, wherein the series of radio link measurements using the evaluation period corresponding to a non-DRX mode is stopped. Determining that the timer has expired;
The method of claim 1, further comprising: determining that a radio link failure has been detected.   The method according to claim 1, further comprising the step of determining the number of measurements during the sleep period based on the measurement time, the synchronization establishment measurement time, a counter value, and a constant.   The method of claim 1, further comprising determining a number of measurements for the series of radio link measurements.   2. The method of claim 1 further comprising the WTRU determining a reference signal quality to determine a radio link failure.   2. The method of claim 1, further comprising the WTRU determining a downlink channel block error rate to determine a radio link failure.   8. The method of claim 7, further comprising the WTRU decrypting a radio network temporary identifier (RNTI).

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